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by Ann Kane Rheault
KINGSTON, RI - A cooperative research project begun two years ago by members of the Rhode Island Lobstermen's Association (RILA) and local scientists is starting to bear fruit, providing the type of biological information that is at the foundation of the egg production models that currently drive lobster management.
Researchers are beginning to use the information gleaned from the cooperative study to shed light on how frequently lobsters molt and on the maturity of female lobsters in Southern New England waters.
In the course of their daily fishing activities over the last two years in the inshore waters of Rhode Island Sound, Block Island Sound, and Narragansett Bay, lobstermen working on 13 boats collected biological data and tagged female lobsters.
In all, nearly 12,000 lobsters were tagged. So far, around 1,000 lobsters have been recaptured. Researchers expect that number to jump after the 2002 fishing season gets going and to continue into the future as lobstermen catch more of the tagged animals.
The study was funded by a $70,508 Saltonstall-Kennedy grant awarded by the National Marine Fisheries Service (NMFS) in 1999.
The project included scientists from the University of Rhode Island (URI) Fisheries Center, Rhode Island Sea Grant Marine Extension, and the Rhode Island Department of Environmental Management's Division of Fish and Wildlife.
Traditional EPR model
URI scientist Kathy Castro urged lobstermen to mail in any tag-return cards they may have been keeping, since the researchers are trying to gather as much information as possible now that they have begun their data analysis.
Castro explained that the NMFS egg-per-recruit model was based on previous studies that describe the female mating pattern as follows.
Mature females molt in the spring or fall and then mate. After mating, they carry their fertilized eggs internally for an unknown time and then externally for nine to 11 months.
The NMFS model assumes that females molt one year and extrude eggs the following year, releasing eggs every other year.
Because the assumption is that these egg-bearing lobsters will not molt during the one-year time period when they have "egged up," molt probability is a key factor used in the egg production models.
Rhode Island lobsterman Bob Smith measures a lobster carapace. Lobstermen participating in the RILA cooperative research project tagged female lobsters with a plastic t-anchor tag and collected biological data including the animals' size before returning them to the water. While saying they found the project informative and would do it again, most of the lobstermen said that the tagging was harder and more time consuming than they'd expected. They suggested that in the future, more boats should be involved in this type of tagging study to spread out the workload. Barbara Somers photo.
Assumptions challenged
However, the actual data collected from the RILA study is hinting that those assumptions may not be valid for lobsters from the inshore Rhode Island waters that are actively fished by lobstermen.
Of the 894 females recaptured so far, nearly 10% had egged up twice in the 12-16 month time period of the study.
But, as Castro pointed out, this doesn't necessarily mean that Rhode Island lobsters are producing significantly more viable eggs than previously thought. Researchers don't know for sure whether those lobsters carried their first batch of eggs to term. They may have dropped the eggs before they were viable due to stress or they may have even extruded unfertilized eggs.
It may also be possible, she said, that some of the females may have mated once and stored the sperm internally to fertilize the second batch of eggs. This has been shown to happen with larger females.
The 85 females that egged up twice ranged in size from just under 3" to around 3-3/4". Around half of those 85 females were about 3-1/2" long, just over the minimum legal size.
Another 80 females egged up once in the 12-16 month period. In all, 34% of the recaptured females extruded eggs, releasing them into the water. Around 49% of all recaptured females had molted, while 40% of them did not molt during the study period.
Shell disease
The lobstermen involved in the tagging study attended training workshops where they learned how to correctly insert the plastic t-anchor tags and v-notch the lobsters' tails.
However, the v-notching portion of the study was discontinued after the first month because of the prevalence of shell disease. The researchers didn't want to take any chances of increasing the likelihood of infection by cutting into the lobsters' shells.
Information on the extent of shell disease was recorded when the lobsters were tagged and also when they were recovered.
Around 33% of the 146 lobsters with shell disease did not molt during the study period. Of these, 48 animals, around 46%, got better, 10% got worse, and 44% stayed the same.
However, roughly 67% of the diseased lobsters did molt during the study. Of the 98 diseased lobsters that molted, around 57% got better, 6% got worse, and 37% stayed the same.
These results make it clear that shell disease can persist and get worse even after the animals shed their old shells and lay down new ones.
Migration
As expected, recaptures followed the fishing season, with more lobsters caught in July and August and the fewest caught in the winter months. So far, around 95 fishermen have contacted researchers by mail or by phone to submit recapture information.
Of the 437 lobsters recaptured in Narragansett Bay, the highest number of individuals, around 29%, traveled in a southerly direction. Those lobsters traveled an average of around six nautical miles, spending an average of 212 days at large.
URI researcher Barbara Somers said the animals tended to migrate out of the warm water of the bay to cooler waters in the summer. Only a few of the lobsters migrated east or west in the waters of Narragansett Bay.
Out in the waters of Block Island Sound and Rhode Island Sound, the highest number of individuals, around 26% of the 478 lobsters recaptured there, had moved in a southeasterly direction, averaging around 17 nautical miles of travel and spending an average of 71 days at large.
Hard work
Somers explained that the RILA participants began tagging in April 2000 and finished in July 2001. Although the original goal was to tag 60,000 lobsters, the final number was only 11,964, she said.
Each of the 13 boats in the study got a box of 2,000 tags, but only one of them managed to use all of them. Most tagged around 500 lobsters.
As the lobsters were tagged, the fishermen recorded their observations on small tape recorders or data sheets and gave that information to the URI researchers monthly. Information on recaptured lobsters was reported by phone or by mail-in cards provided to every boat in the fleet.
A special easy-to-use lobster gauge was also distributed to local fishermen to help them quickly measure the tagged animals. When the study ended, the researchers sent the RILA participants a questionnaire to get feedback and got responses from six of the 13 boats involved.
Most lobstermen said that the tagging was harder and more time consuming than expected. They suggested that in the future, more boats should be involved in this type of tagging study to spread out the workload.
Nevertheless, all the participants who responded to the questionnaire said they found the project informative and would do it again.
Lobsterman Jeff Jordan said that it was more difficult to tag the lobsters while trying to do his own work than he thought it would be when he signed on.
However, he noted that when Somers came out on his boat one day she managed to tag 500 animals, compared with the 25 or so that he could manage in the course of a day.
Jordan suggested that future studies might have a team of taggers move around the fleet and work alongside lobstermen to get more tags in the water early on and to lessen the burden on the fishermen.
Nonetheless, he recognized the value of the collaboration.
"More and more people will see that this is the future and that this information is crucial," Jordan said.
Collaboration key
Cooperative efforts like the RILA study use the strengths of the fishermen and the scientists to everyone's best advantage, according to Castro.
The fishermen, who have daily contact with many lobsters over a wide geographic area and have the boats, equipment, and expertise needed to catch and handle the lobsters, are ideal candidates for carrying out the tagging and recapturing tasks.
The scientists, on the other hand, lend their expertise to the design and data analysis portion of the study. They are just starting to take the information gathered by the fishermen and draw conclusions on lobster growth, molting probability, migration patterns, and fecundity that they hope will be used in the next lobster stock assessment.
Castro explained that cooperative research projects like this one also allow the fishermen to share responsibility for co-managing the lobster resource through their investments in time and effort.
When fishermen better understand the biology of the species they're fishing for, they can better appreciate the science involved. This enhances communication and forges a true partnership between scientists and fishermen, she said.
"Even though it's harder to work with data collected by many other people," Castro noted, "if you can find out where the mistakes are and work on minimizing them, these are extremely valuable studies."
Castro hopes to see more cooperative research between fishermen and scientists in the future.
"We can't do it all," she said.
